1. Technical Field
The present invention relates generally to a differential for driving vehicle axles and, in particular, to a fluid actuated locking type differential.
2. Description of the Prior Art
Differentials for driving axles are known and typically include a set of gears coupled between two half axles. Such a differential enables the driven axles of the vehicle to rotate at different speeds and equal driving force can be transmitted to driving wheels associated with each axle. Under certain conditions, the differential has a disadvantage if one drive wheel is on a slippery surface, such as ice or mud. The wheel on the slippery surface will slip and spin because its associated tire cannot grip the surface.
A limited slip differential was designed to improve the traction of a vehicle wheel on the slippery surface. This is done by allowing the differential to transmit torque to the axles in unequal amounts without interfering with the differential action on turns. The most common limited slip differential is a friction type which has clutch assemblies mounted between the two side gears and the differential case. Clutch assemblies transfer torque from the slipping and faster spinning wheel to the slow spinning good traction wheel. Typically the clutch assembly has disks that are splined to the side gear and has plates that fit into the differential case. The disks rotate with the side gear and the plates rotate with the case.
A locking differential was developed to overcome a limited ability on the part of the limited slip differential to transfer torque between axles. Such locking differential typically includes a fluid actuated piston for applying force to a clutch assembly located between case and a side gear. Pressurized fluid is provided to a piston cavity by means of at least one radially extending passage formed in a differential case half which leads to an opening on the outer surface of the case half hub. A ring-shaped manifold is fitted external to the case half and suitably mounted so that it does not rotate to deliver fluid to the opening in the case half.
The fluid is typically pressurized to a relatively high pressure which acts on all passage surfaces in the manifold and case half. The fluid pressure acting on the surfaces often causes a relative cocking or misalignment between the manifold and case half which can cause premature wear and even failure of the manifold, case half or seals located therebetween.
The fluid used to actuate the piston is typically different than a lubricant located in a housing for the differential which is used to cool and lubricate gears and bearings of the differential. Thus, it is very desirable to maintain the actuating fluid separate from the differential lubricant. If the seals wear prematurely due to the relative misalignment between the manifold and case half or fluid leakage occurs for other reasons, mixing of the actuating fluid and differential lubricant can occur and degrade the lubricant.